Electric motor



NOV. 3, A E' OSWALD ELECTRIC MOTOR 2 Sheets-Sheet l Filed Dec. 31, 1929www/a4 @f A #or j.

Nov. 3, 1931. v A. E. oswALD 1,829,872

ELECTRIC MoToR Filed neo. 31. 1929 2 sheets-sheet 2 #wen/0r:

f/Urn Patented Nov. 3, 1931 UNITED STATES PATENTk OFFICE ALFRED E.OSWALD, `OF EACKENSACK, NEW JERSEY, ASSIGNOR T UNDERWOOD ELLIOTT FISHERCOMPANY, OF YORK, N. Y., A CORPORATION OF DELAWARE ELECTRIC MoronApplication 'lled December 31, 1929. Serial No. 417,620.

This invention relates to electric motors for driving machines whereconsiderable variations in speed are desired, also to motors intendedfor use on circuits having different characteristics, and moreespecially to compound wound shunt motors for driving small machines,such as typewriters, calculating machines, etc. e

This invention provides a type of motor applicable also for use Where itis desired to drive machines havin different torques at a given normalspeed, t at is, where the work to be done by the motor varies in itsapplication from one machine. to another.

Another feature of this invention is the production of motors for use ondifferent machines to be run at a` given speed, the machines havingvarious speed reductions, and which machines are not therefore suited tobe driven by va motor having a fixed speed, such as an ordinary directcurrent shunt motor. v

Another feature lies in the fact that motors embodying this inventionoperate at different speeds on vdirect current with the characteristicof an ordinary shunt motor, that is, they maintain given speeds withinsmall limits at all different loads. This feature'does away with theusual method of yinterpolating a rhcostat in series with the armaturewherein the speed `of the motor cannot be maintained constant as it is afunction of the torque of the motor. y

Another feature lies in the great range of speed for which the motorsmay be. adjusted and operated. It has been found, in practice, forexample, that a motor embodying this invention can be adjusted to varyin speed from 1200 to 2500 revolutions per minute, whereas in motors notbuilt along the lines of this disclosure, the speed cannot be varied, byshifting the brushes, more than from 1200 to about 1500 revolutions perminute without excessive sparking of the brushes at the commutator.

Another feature lies in the fact that rheostats and other auxiliarydevices generally interpolated inthe leads of the motor to vary thespeed are entirely done away with so that 'the motor is self-containedand complete in itself Without resorting to any such devices to controlits speed. f

Another feature relates to the provision of a numberof main field-coils,connected across the main brushes, and auxiliary coils connected acrossa pair of auxiliary brushes, the latter mounted midway between the mainbrushes on the commutator and co-operative with the main field-coils tocontrol the motorspeed. The auxiliary field-coils operate to build up orhinder the magnetic flux of the main field-coils by the reversal ofcurrent passing through them by the act of shifting the auxiliarybrushes around the commutator to a greater or less extent, either sideof a neutral line. This neutral line passes diametrically through thearmature from the center of one pole to the center of the other,

and when the auxiliary brushes occupy this Y position no current flowsthrough the auxiliary coils.

Another feature of this invention lies in the fact that as the brushesare shifted on the commutator the strength of the auxiliary l in theability to adjust motors to compensate n for deviations from the normalvoltage, so that the motors will run on different voltages at the properspeed to do the work. n

Another feature of the invention consists in so connecting the variousfield-windings to main and auxiliary brushes that as the brushes areshifted in the direction of armaturerotation, for example, to slow downthe motor, according to the well-known law, the voltage onthese windingsis increased by that act to strengthen the field and still furtherslowthe motor down, and vice versa.

In this motor the variations, in the resultant ma etic flux of thefield, are obtained artly rom the auxiliary field-windings belngeffective to boost or oppose the main fieldflux and partly from thechange of voltage at the terminals of the shunt field. If the auxiliarybrushes are mounted in the neutral position shown in Figure 5, the motorwill be running, at its average speed, with no current passing throughthe auxiliary lieldcoils.

The embodiment of this invention is sinnlar in a number of respects tothe construction of the motor disclosed in my Patent 1,554,641? ofSeptember 22, 1925, wherein a cylindrical field-structure is formed ofannular laminations upon which are mounted main and also auxiliaryfield-coils, and vfherein a head at one end of the motor-casing issupplied With a terminal plate and ay converter-plate, the latter havinginterchangeable connections to accomplish the different functions forwhich the motor is applicable. 1n the present invention by using fourdilterent converter-plates and only tivo motors, one Wound for 110 voltsand the other wound for 220 volts, it is possible to adjust the motorsfor use not only on direct current and alternating current circuits atdifferent voltages, but also when used on alternating circuits, themotors can be used on all frequencies from 25 to GO cycles, and by usingadditional converter-plates still further adaptations can be madeaccording to the practical requirements.

Other features and advantages will hereinafter appear.

In the accompanying` drawings,

Figure 1 is a top view of the assembled niotor With a portion of thecasing cut away.

Figures 2, 3 and -1 show the converter-plate and its connections, andthe direction of the current and the direction of the magnetic flux ineach held-coil when the motor is adjusted to run at medium speed, fastspeed and slow speed. respectively. Figure il is a line diagram, andcorresponds with Figure 2, for medium speed.

Figure 5 is an end view of the motor with one head removed, showing themain and auX- iliary coils mounted on the annular eldstructurelaminations. This vieuT shows the brushes in the medium-speed position.

Figure 6 is similar to Figure 5, with the brushes shown in thefast-speed position.

Figure 'T is similar to Figure 5, .vith the brushes in the slow-speedposition.

Figure 8 shows the right-hand end of the motor, as shown in Figure 1,having the main and auxiliary brushes mounted thereon.

The armature 55 of the motor 56 has a commutator 2G. and a shaft 27which rotates in heads or end-enclosures 28, 29, secured to acylindrical tubular casing 30. lThe head 29 has a pair ofdiametrically-spaced main brushes 19 and 20, Figure S, and a 4pair ofsimilarly-spaced auxiliary brushes 22 and 23, each of which is connectedto contacts 91 on a terminal plate The line of the main brushes isperpendicular to that of the auxiliary brushes. lThe held-structureincludes laminations 31 of U shape, each lamination forming` half of thefield-structure, the two halves of the field-structure being symmetricaland composed of the same shaped laminations, and each half forming apole-piece for the motor. The arms of each lamination have at their endslingers and ogs 33 and 32, respectively, which interdigitate Withsimilar ogs and fingers on the other half of the structure, so that t-heield-laminations are interloclred at the joints to produce paths for themagnetic lines of force of minimum resistance. Main field-coils 49 and5() are mounted on the upper pole-piece of the laminatedfield-structure, while similar coils 51 and 52 are mounted on the lowerpole-piece of the field-structure. The coils L19, 50, 5l, and 52constitute the shunt field-coils of the motor. Additional field-coils 6Gand (3T are mounted on the arms of one side of the lower and upper halfof the field-structure, respecively, While coils v and 71 are mounted onthe opposite side on corresponding arms of the saine. The coils GT and70 constitluif.` thc series field-coils of the motor While coils ($6 and71 constitute the auxiliary field-coils of the same. The terminals ofall of these coils are severally connected to the contacts 91 on theterminal plate S3, as shown in Figure 5. A converter-plate 96 has clips92 thereon for engaging the contacts 91, ou the terminal plate 88, andconductors 9S thereon connecting the various terminals 90 in accordancewith the diagrams shown in Figures 2. 3 and 4.

It is understood. of course. that the diagrams shown in Figures 2. 3 and4 are illustrative of but one scheme of connections, and would beapplicable to adjust the motor for use to meet a given set ofconditions. Various plates may be supplied for interchangeable use withthe motor. so that it can be used under a Itreat number of differentconditions; the various plates havin;r different connections thereon forvai-ving the connections of the several coils in the motor: for example,a motor Wound for use on 110 volts may have not onlyT a plate to adjustit for use on direct current 110 volt installations. but another plateto adjust it for usc on 160 volts 42 cycle alternating current; or, as afurther illustration, the same motor may be adjusted by the use of othersuitable converter-plates for operation on different frequencies, oneplate for 25 or 80 cycles, another plate for 40 cycles, another for 50to G0 cycles, and so on. Use of the motor for different purposes will beunderstood from said Patent 1,554.647.

It is seen from the above that the motor is Capable of universal use, asit can be adjusted for circuits having different voltages an-dfrequencies, and for operating at different speeds under each condition,the plates being selected to meet the condition of speed and the circuitto be used, while the shifting of the brushes cti-operates therewith toinfluence further the speed of the motor.

Plates 96 and 83 are mounted on the head 28. The heads 28 and 29 aresecured together by suitable bolts 39 and 41 which screw into a block 40secured to the casing 30. The head 29 has two slots 38, Figure 8, eachof which may receive the screw 39. When the screws 39 are loosened, thehead 29 can be rotated to shift the brushes on the commutator 26 by theoperator bymeans of a handle 42. Screws 53, one each side of the screws39, hold the latter in position while the head is being rotated.

By rotating the head 29, the brushes 19, 20, 22 and 23 are shiftedsimultaneously on the commutator and the speed of the motor is increasedor decreased correspondingly, depending upon the direction the brushesare shifted with reference to the direction of the armature-rotation.The casing 30, Figure 1, is provided with markings 8() to indicate tothe operator which direction to rotate the head 29 to control the speedof the motor. According to the diagram of connections shown in Figures2, 3 and 4, the current from the positive side of the mains passesthrough the series field-coils 7() and 67, connected in series, to thepositive main brush and from the negative main brush to the negativeside of the line. The current through the shunt field-coils passes fromthe auxiliary brush 22 through coils 51, 50, 49 and 52 connected inseries, and then to the negative side of the line at main brush 19. Theauxiliary field-coils 71 and 66 are connected in series, and at theirouter terminals across the auxiliary brushes 22 and 23. When theauxiliary brushes are in a vertical position, as shown in Figure 5,there is no difference of potential to generate any current in theauxiliary field-coils 71 and 66, and the motor is then running, asalready stated, similarly to a simple compound shunt-wound motor, withthe exception. however, that the shunt fieldcurrent. passing throughthecoils 49 to 52,

' is taken, in the present invention from the armature-windings betweenthe auxiliary brush 22 and the main brush19. These windings operate on apotential of approximately 50 volts, for example, on a` 110-volt circuit(assuming there is a 10-volt drop in the series coils 67 and 70),instead of operating on the full-line potential of 110 volts, asheretofore.

If it is desired to slow down, the motor .from the average speedresulting from the position of parts shown in Figure 5, a clockwiseshifting of the brushes, in the direction of the armature-rotation, willbring about the condition shown in Figure 7, wherein the voltage acrossthe auxiliary brushes 22 and sends current through the auxiliary coils71 and 66, to produce magnetic lines of force in the same direction theother field coils, with the eect that the strength of the magnetic fluxis increased and the speed of the motor is lowered.

If, however, the speed of the motor is to be increased from the normalresulting from the position of parts shown in Figure 5, then therotation counterclockwise of the brushes Will cause a current to flowthrough the auxiliary windings 71 and 66 in the opposite direction tothe above, and the magnetic flux of the coil-s 71, 66 will oppose thefield of the remaining field-coils so that the strength of the magneticflux of the field is weakened thereby, and the motor is caused to speedup as shown in-Figure 6. When the auxiliary brushesk are shifted acrossthe neutral position, Figure 5, either from the right or from the left,the direction of the current in the auxiliary coils 71 and 66 reverses,as indicated by the plus and minus signs as applied to the auxiliarybrush-terminals 22 and 23, shown in Figures 3 and 4.

The shunt field-coils 49 to 52, connected across the .auxiliary brush 22and main brush 19, are -supplied with current, the amount of which alsodepends upon the position of the brushes, it being understood, ofcourse, that in the position shown in Figure 7, the shunt field-coilswill have their' maximum current, while, in Figure 6, the shuntfieldcoils will have the minimum current corresponding with the minimumand maximum speeds of the motor, respectively.

It is seen from the above that this motor operates by combining threedistinct principles of motor-speed regulation. In the first place thebrushes are shifted and the speed of the motor responds theretoaccording tothe well-known law that a motor slows down as thefield-brushes are shifted in the vdirection of rotation of the armature,and

vice versa. Second, as the brushes are shifted above to change the speedof the motor, the auxiliary field is strengthened or weakened by reasonof the auxiliary fieldwindings (through which no current at all passesat normal speed), having current pass in one direction to slow down themotor and in another direction to speed up the motor; and,third,strengthening or weakening of the flux of the field is obtained bymeans of controlling the electromotive force applied at the terminals ofthe shunt field-coils.

All three of these speed-controlling features are co-operative in thisdisclosure to bring about the desired speed of the motor and arecontrolled by the single act of shifting all of the brushes on thecoinmutator through the same angular distance.

The angle through which the brushes may be shifted, and, therefore, thegreatest amount of change in speed obtainable, depends upon the shapeand the position of the pole-pieces. Pole-pieces which do not extendaround tle armature to such an extent as others have, within certainlimits, a

ymain brushes` all the brushes beine; e uall7 i e, J

spaced around the commutator, means for securing the brushes in spacedrelation and tor shitting the same on the eon'nnutator, seriesheld-coils connected to one main brush in series with said armature,auxiliary lieldcoils connected across the auxiliary brushes, shuntlield-coils connected across .a main brush and an auxiliary brush, andmeans tor shitting all tne brushes to vary the strength ot the lield andcontrol the speelL ot the motor.

ln an electric motor, an armature, a commutator theretor, aheld-structure, a pair of main brushes, pair orp auxiliary brushes,series {leid-coils connected, in series with the armature, to one ot themain brushes, auxiliary .held-coils connected across the auxiliarybrushes, shunt coils connected across the other main brush and anauxiliary brush, and means tor shifting all the brushes the same. amountin the same direction, the brushes to which said shunt coils areconnected being shift-able from a position having lield and speed up themotor.

fi. in an electric motor, an armature, a coinmutator therefor, alield-structin pair ot main brushes, a pair et' auxilia brushes,

series held-coils connected, in series with the armature, to one of themain brushes, auxiliary field-coils connectedacrossthe auxiliarybrushes, shunt coils connected across t ie other main brush and anauxiliary brush, and means tor shitting all the brushes the same :leuntin the saine direction, the brushes to which said shunt coils areconnected being shittable from a position having a given potential to aposition ha fing greater potential as the brushes are shift-ed in thesame direction as the direction ot revolution ot the armature, ettectiveto strengthen the tield and slow down the motor.

l. ln an electric motor, an armature, a coinmutator, a pair et mainbrushes, a pair ot auxiliary brushes, each brush of a pair mountedbetween the brushes of the other pair, a lieldstructure including ser'escoils, shunt coils and auxiliary coils, the series coils y,beingconnected in series with the main brushes. *l*

LLL

auxiliary coils being connected across the aux ili ary brushes, and theshunt coils being con nected across an auxiliary brush and a main brush,and means for shitting all the brushes on the commutator simultaneously,whereby the operations ot the auxiliary and shunt coils are caused tooppose or aid each other to create the field of the motor by changingthe direction of currentl in theauxiliary coils, whereby the strength ofthe field is modified to regulate the speed of the motor.

5. In an electric motor, an armature, a conlmutator, a pair ol mainbrushes, a pair ot auxiliary brushes, each brush ot' a pair mountedmidway between the brushes of the other pair, a held-structure includingseries coils, shunt coils and auxiliary coils, the series coils beingconnected in series with the main brushes, the auxiliary coils beingconnected across the auxiliary brushes, and the shunt coils beingconnected across an auxiliary brush and a main brush, said auxiliarycoils being positioned normally in the field so that no current 'llowstherethrough, and means supporting all the brushes for shitting the samesimultaneously on the commutator in either direction from said normalposition, effective to position the auxiliary brushes to cause currentto flow through the auxiliary coils in either direction at will, and tomodify concomitantly therewith the current through the shunt coils tocooperate with the auxiliary coils, to in- {iuence the magnetic tlux ofthe field and thereby control the speed of the motor.

6. In an electric motor, an armature, a commutator, a pair ot mainbrushes, a pair of auxiliary brushes, each br sh ot' a pair mountedbetween the brushes oit the other pair. a lieldstructure includingseries coils, shunt coils and auxiliary coils, the series coils beingconnected in series with the main brushes, the auxiliary coils beingconnected across the auxiliary brushes, and the shunt coils beingconnected across an auxiliary brush and a main brush, and means foradjusting the brushes on the connnutator, the magnetic tlux of theseries field-coils being in the same direction as the magnetic flux ofthe shunt field-coils, the magnetic in'liuence ol' the auxiliarytieldcoils operating in the same direction as the flux of the shunt andseri-es held-coils when the auxiliary brushes are adjusted in onedirection, and in the opposite direction when the auxiliary brushes areadjusted in the opposite direction, eli'ective to control the strengthet' the resultant magnetic flux ot' the lield and thereby control thespeed ot the motor.

ALFRED E. OSWALD.

